Turning to FIGS. 1 and 2, an example of a conventional system 100 can be seen. System 100 generally comprises a touch panel 102 and touch panel controller 104. The touch panel 102 has an array of sensors formed by a set of column electrodes (e.g., electrode 103), where each electrode of each column is coupled together by a strip electrode (e.g., strip electrode 107), and a set of row electrodes (e.g., electrode 109), where each electrode of each row is coupled together by a strip electrode (e.g., strip electrode 107). Usually, the column and row electrodes (e.g., electrodes 103 and 105) are formed in two separate layers with a dielectric or insulating layer formed therebetween, and these conductive layers which form the electrodes (e.g., electrodes 105 and 109) are generally transparent to visible spectrum light (e.g., light having a wavelength from about 380 nm to about 750 nm). The strip electrodes for each column (e.g., strip electrode 107) are then coupled to the interface or I/F 106 of the touch panel controller 104 by terminals X-1 to X-N, while the strip electrodes for each row (e.g., strip electrode 109) are coupled to the interface 106 by terminals Y-1 to Y-M. The interface 106 is able to communicate with the control circuit 108. As shown in greater detail in FIG. 2, the interface 106 is generally comprised of a multiplexer or mux 202 and an exciter 204.
In operation, the interface 106 (which is usually controlled by the control circuit 108) selects and excites columns of electrodes (e.g., electrode 103) and “scans through” the rows of row electrodes (e.g., electrode 105) so that a touch position from a touch event can be resolved. As an example, interface 204 can excite two adjacent columns through terminals X-j and X-(j+1) with excitation signals EXCITE[j] and EXCITE[j+1], and interface 106 receives a measurement signal from a row associated with terminal Y-i. When an object (e.g., finger) is in proximity to the touch panel (which is generally considered to be a touch event), there is a change in capacitance due at least in part to the arrangement of electrodes (e.g., electrodes 103 and 105), and the controller 108 is able to resolve the position of the touch event.
Most conventional touch panels (e.g., touch panel 102) do, however, exhibit a non-uniform response characteristic, which is manifested as non-uniform signal strength across the panel. This non-uniformity is generally caused by natural variations in the patterns forming the column and row electrodes (e.g., electrodes 103 and 105). In other words, the electrodes are arranged to have gaps or non-overlapping regions between the electrodes so that, as an object (e.g., finger) traverses the panel (e.g., panel 102) and passes over these non-overlapping regions, the signal strength or measured capacitance changes. Therefore, there is a need for a touch panel having a more uniform response characteristic.
Some examples of other conventional systems are: U.S. Patent Pre-Grant Publ. No. 2011/0095996; U.S. Patent Pre-Grant Publ. No. 2011/0095997; U.S. Patent Pre-Grant Publ. No. 2011/0102361; and U.S. Patent Pre-Grant Publ. No. 2011/0157079.